In the Linux kernel, the following vulnerability has been resolved: power: supply: bq256xx: Fix...

In the Linux kernel, the following vulnerability has been resolved:

power: supply: bq256xx: Fix use-after-free in power_supply_changed()

Using the devm_ variant for requesting IRQ before the devm_ variant for allocating/registering the power_supply handle, means that the power_supply handle will be deallocated/unregistered before the interrupt handler (since devm_ naturally deallocates in reverse allocation order). This means that during removal, there is a race condition where an interrupt can fire just after the power_supply handle has been freed, but just before the corresponding unregistration of the IRQ handler has run.

This will lead to the IRQ handler calling power_supply_changed() with a freed power_supply handle. Which usually crashes the system or otherwise silently corrupts the memory...

Note that there is a similar situation which can also happen during probe(); the possibility of an interrupt firing before registering the power_supply handle. This would then lead to the nasty situation of using the power_supply handle uninitialized in power_supply_changed().

Fix this racy use-after-free by making sure the IRQ is requested after the registration of the power_supply handle.